• The Korean Journal of Pesticide Science
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• v.7 no.4
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• pp.288-295
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• 2003

To determine the mechanism of the resistance to organophosphorus insecticide, chlorpyrifos, in diamondback-moth (Plutella xylostella L.), activities of esterases, glutathione-S-transferase (GST) and AChE insensitivity which were known for causing factor of resistance were measured. Also, the relationship between AChE insensitivity and the resistant ratio was investigated to inquiry the cross-resistance. The resistant ratio of chlorpyrifos-resistant strain (CRS) of diamondback-moth at the 6th generation was developed 160 fold compared to susceptible strain (SS) one. Activity of GST that are extracted from CRS was 1.7-fold higher than that from SS. However, activity of total esterases from CRS was similar to that from SS. In AChE insensitivity test, CRS was 11.8-fold less sensitive than that from SS. CRS was ranged from 17.6 to 33.6-fold less sensitive than SS to other insecticides having same target site with chlorpyrifos such as dichlorvos, dimethylvinphos and carbofuran. Insensitivity of AChE to phenthoate-oxon, however, was 1.7-fold. Resistance of CRS was 82-fold, 47-fold and 42-fold higher than SS to dichlorvos, dimethylvinphos and carbofuran, respectively, but 2.3-fold to phenthoate and then we could identify that the resistance development of insecticide might have a lot of difference among the chemicals with the same target site. The relationship between the AChE insensitivity and the resistant ratio was significantly correlated$(r=0.9951^{**},\;p^{(0.01)}$. This result indicates that AChE insensitivity was associated with insecticide resistance. Overall, these results suggest that insensitivity of AChE was an important factors to chlorpyrifos resistance in diamondback-moth, and the slightly increased activity of GST may also have contributed to that.

• Korean journal of applied entomology
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• v.31 no.1
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• pp.1-6
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• 1992

These studies were carried out to compare toxicological test methods of two spotted spider mite, Tetranychus urticae Koch,; and to investigate relationship between in vivo resistant level of highly acaricide-selected population, and in vitro insensitivity of the AChE in the same population to carbophenothion and ethion. The slide dip method (CV = 8.7%) was of more accuracy and suitability than that of the leaf dip method(CV=12.2%) and leaf disc method (CV= 13.6 %) in determination of the resistant levels of twospotted spider mite to acaricides. The slide dip method also had the advantages of simple treatment with different populations on a slide at the same time, standardization of post-treatement conditions and living plants exclud¬ed from the test. Even though the topical application method(CV =8.1 %) showed high accuracy, it had the demerits of the much time consuming, need of expensive equipment and difficulty of test manipulation. For a limited time, the 22nd successive carbophenothion-selected population of two-spotted spider mite showed 156- and 128-fold resistant levels to carbophenothion and ethion(both alPs), respectively. However, the 24th successive ethion-selected population revealed 64.1- and 65-fold resistant levels to ethion and carbophenothion, respectively. In the inhibition of AChE activity, the carbophenothion-selected population showed 3.3- and 2.7-fold insensitivity in AChE activity to carbophenothion and ethion, respectively. Likewise, the ethion -selected population exhibited 3- and 2.6-fold insensitivity in AChE activity to carbophenothion and ethion, respectively, as compared with that of susceptible population. As a result, a good relation was recognized between in vivo resistance to organophosphorous acaricides and in vitro insensitivity of the AChE to corresponding inhibitors.

• The Korean Journal of Pesticide Science
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• v.10 no.1
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• pp.50-55
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• 2006

A field-resistant strain of the diamondback-moth(Plutella xylostella L.), collected from Chinese cabbage alpine farmland at Gangwon-do, Korea, was used for determination of the characteristics of resistance to chlorpyrifos using the activities of esterases and glutathione-S-transferase(GST), protein sequestration and AChE insenstivity. Although the activities of esterases extracted from resistant strain and susceptible strain were not significantly different, isozyme bands shown on the electrophoresis were different. GST activity from field resistant strain was 1.5-fold higher than that of susceptible. No differences were shown between resistant and susceptible ones in protein sequestration. The insensitivities of AChE to chlorpyrifos, however, extracted from susceptible strain was 460-fold higher than those of resistant. These results indicated that the insensitivity of AChE is the major factor for developing the resistance and activities of GST might be a minor factor.

• Korean journal of applied entomology
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• v.30 no.2
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• pp.117-123
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• 1991

Acetylcholinesterase(AChE) and esterase activities as mechanisms of resistance to fenobucarb, carbofuran and diazinon in the insecticide-selected brown planthopper strains were investigated. Although there was no significant difference in AChE activity from suscept tible and resistant strains, AChE insensitivity was highly increased in the carbam없e insecticide-selected strains. On the other hand, esterase activity was moderately increa잃d in all the s selected strains. It is concluded that the cross-resistance and the level of resistance in the b brown planthopper can be explained by the combination of altered AChE and high esterase a activity, although a possible involvement of other factor(s) can not be excluded.

• The Korean Journal of Pesticide Science
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• v.7 no.1
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• pp.18-24
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• 2003

The activities of esterase and acetylcholinesterase(AChE) on the Diamond backmoth (DBM), Plutella xylostella (Lepidoptera: Yponomeutidae) and Beet armywarm (BAW), Spodoptera exigua (Lepidoptera: Noctuidae) and inhibitions of AChE with flupyrazofos were clarified from the results of a series of experiments. These findings are described in brief as follows. The AChE activities of DBM and BAW in heads were $1.5{\sim}11.1{\mu}$mol/g/min in $1st{\sim}4th$ instar larvae of DBM and $1.7{\sim}45.2{\mu}$mol/g/min in $1st{\sim}6th$ instar larvae of BAW, respectively. Those were $25{\sim}30$ times higher in above 4th instar larvae of BAW than that of the 1st instar larvae of DBM. The activities of aliesterase in heads were $1.7{\sim}4.7$ times higher in $2nd{\sim}4th$ instar larvae of DBM and $8{\sim}55$ times higher in $3rd{\sim}6th$ instar larvae of BAW than 1st instar larvae of DBM. In abdomens, those were $3{\sim}17$ times higher in $2nd{\sim}4th$ instar larvae of DBM and $12{\sim}30$ times higher in $3rd{\sim}6th$ instar larvae of BAW than 1st instar larvae of DBM. Median AChE inhibition concentration $(I_{50})$ of flupyrazofos to the 2nd instar larvae of DBM and BAW were 92 nM and $15{\mu}M$, respectively, and those to the 4th instar larvae of DBM and BAW were $1.8{\mu}M$ and 3.1 mM, respectively. Insensitivity ratio of flupyrazofos in the 2nd instar BAW larvae showed ca. 162 times higher than that in the 2nd instar larvae of DBM, and that of the 4th instar BAW larvae showed ca. 1,720 times higher insensitivity to flupyrazofos than that of the 4th instar DBM larvae. AChE activities in the 2nd instar larvae of DBM and BAW at 32 h after applicaton of flupyrazofos decreased from 67.6% to 32.4% of the activity of the untreated control. That of the 4th instar larvae of DBM increased for 0.5 h after application flupyrazofos up to 75% of the untreated control, and after that it decreased to 34.5% of the untreated control at 32 h. In contrast, in the 4th instar larvae of BAW AChE activities increased for 8 h gradually up to 102 % of the activity of the untreated control, and then the activity decreased to 97% of the untreated control at 16 h after treatment.